Wireless communication devices, such as cellular telephones and other personal communication devices, enjoy widespread use. Because of their portability, such devices are finding use in very noisy environments. Users of such wireless communication devices often find that unwanted noise seriously detracts from clear communication of their own speech. A person with whom the wireless system user speaks often has a difficult time hearing the user's speech over the noise.
Wireless devices are not the only communication systems exposed to unwanted noise. For example, video teleconferencing systems and multimedia computer communication systems suffer similar problems. In the cases of these systems, noise within the conference room or office in which such systems sit detract from the quality of communicated speech. Such noise may be due to electric equipment noise (e.g., cooling fan noise), conversations of others, etc.
Directional microphone arrays have been used to combat the problems of noise in communication systems. Such arrays exhibit varying sensitivity to sources of noise as a function of source angle. This varying sensitivity is referred to as a directivity pattern. Low or reduced array sensitivity at a given source angle (or range of angles) is referred to a directivity pattern null. Directional sensitivity of an array is advantageously focused on desired acoustic signals and ignores, in large part, undesirable noise signals.
While conventional directional arrays provide a desirable level of noise rejection, they may be of limited usefulness in situations where noise sources move in relation to the array.